Crankcase breech detection for boosted engines

Abstract

Methods for indicating whether a crankcase of an engine is breeched are provided. One example method comprises restricting a communication of the crankcase with atmosphere, acting to increase or decrease a crankcase pressure, and indicating whether the crankcase is breeched based on the crankcase pressure. Another example method comprises sensing a crankcase pressure component, and indicating whether the crankcase is breeched based on the crankcase pressure component, the crankcase communicating with atmosphere via a conduit, a restrictedness of the conduit responsive to one or more of a crankcase pressure and a signal from an electronic control unit of the motor vehicle. Still other examples provide more particular methods for indicating whether the crankcase is breeched, and example configurations that enable the various methods.

The invention claimed is: 
     
       1. A method for indicating whether a crankcase of an engine system is breeched, the engine system comprising an electronic control unit and a positive crankcase ventilation (PCV) system, the method comprising:
 sensing an alternating component and a steady state component of crankcase pressure; and 
 if an amplitude of an oscillation of the alternating component of crankcase pressure correlated to an operational state of an engine cylinder or a turbocharger is below a threshold, indicating that the crankcase is breeched and initiating a mitigating action. 
 
     
     
       2. The method of  claim 1 , wherein the mitigating action comprises one or more of reducing an intake of air into an engine, limiting a torque of the engine, limiting a fuel injection amount supplied to the engine, limiting a throttle opening, and disabling a turbocharger. 
     
     
       3. The method of  claim 1 , wherein the mitigation action includes adding lubricant to the crankcase by pumping lubricant from an auxiliary reservoir and into the crankcase. 
     
     
       4. The method of  claim 1 , further comprising sensing a phase locked sub-component of the alternating component of the crankcase pressure comprising synchronizing a sampling of the crankcase pressure to an operational state of the engine system. 
     
     
       5. The method of  claim 1 , further comprising adjusting restriction of a communication of a valve cover of the crankcase with atmosphere prior to sensing crankcase pressure. 
     
     
       6. The method of  claim 5 , wherein a restrictedness of a conduit is responsive to a pressure measured at a pulsation sensor on a breather valve. 
     
     
       7. The method of  claim 1 , further comprising sensing an additional component of crankcase pressure and the additional component is one of a low-pass filtered pressure, a Fourier component, or a sub-component of the alternating output locked in phase with an operating condition of an engine. 
     
     
       8. The method of  claim 1 , wherein the threshold depends on characteristics of one or more flow-control elements provided in the PCV system. 
     
     
       9. The method of  claim 1 , further comprising determining a size of a breech based on an amplitude of an oscillation of the alternating component of crankcase pressure. 
     
     
       10. An engine system having a crankcase and configured to indicate whether the crankcase is breeched, the engine system comprising:
 a sensor having an alternating output responsive to a crankcase pressure; 
 a check valve disposed in a breather conduit; and 
 an electronic control unit configured to sample the alternating output and to indicate that the crankcase is breeched if one or more oscillations of the alternating output correlated to an operational state of the engine more closely matches an output expected for a breeched crankcase than an output expected for an unbreeched crankcase, the crankcase communicating with atmosphere via the breather conduit connected to a valve cover, adjusting a restrictedness of the breather conduit responsive to one or more of the crankcase pressure and a signal from the electronic control unit. 
 
     
     
       11. The engine system of  claim 10 , wherein the electronic control unit is configured to determine a size of a breech based on one or more oscillations of the alternating output correlated to an operational state of the engine. 
     
     
       12. The engine system of  claim 11 , wherein the restrictedness of the breather conduit is controlled by a breather valve comprised of two check valves. 
     
     
       13. The engine system of  claim 11 , wherein the alternating output is filtered and indicating a breech when the filtered alternating output exceeds one or more of two thresholds.